Axial piston engine

ABSTRACT

An axial piston engine ( 1 ), including a housing ( 2 ) in whose inner compartment ( 4 ) a cylinder drum ( 17 ) and a swash plate ( 26 ) located axially adjacent thereto are situated. Several piston bores ( 21 ), which extend approximately parallel to the central axis of the cylinder drum ( 17 ) are located in the same, pistons ( 23 ) being displaceably guided in the piston bores. The ends of the pistons facing towards the swash plate ( 26 ) are supported on the swash plate ( 26 ). A driving shaft ( 7 ) is rotatably mounted in the housing ( 2 ) and is connected to the cylinder drum in a fixed manner secured against rotation therebetween by a multitooth coupling ( 19 ) comprising teeth ( 43   a   , 44   a ) and tooth spaces ( 43   b   , 44   b ) which alternate regularly in a peripheral direction and which engage with each other. At least one feedthrough channel ( 45 ) which extends essentially parallel to the axis of rotation of the drive shaft ( 7 ) and from one side of the multitooth coupling ( 19 ) to the other is located in the area of the multitooth coupling ( 19 ). Obtained is a flow feedthrough and/or a mechanical feedthrough from one side of the multitooth coupling to the other while ensuring that the multitooth coupling is stable and simple to produce. To this end the feedthrough channel ( 45 ) is located between at least one tooth crown or tip surface (43 d ) and a tooth space bottom ( 444 ) located opposite thereto.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an axial piston engine which, while affording astable construction, provides for a multitooth coupling facilitating afluid flow penetration and/or mechanical penetration between oppositesides of the multitooth coupling.

An axial piston engine of said type is described in DE 32 22 210 A1.

2. Discussion of the Prior Art

In axial piston engines it is known to utilize the housing interior asan intermediate collecting container for leakage fluid. In the operatingmode of the axial piston engine, in the housing interior a specificamount of leakage oil collects, which is under low pressure and flowsoff through a discharge gap or discharge channel to a tank. The leakagefluid situated in the housing interior may be used to lubricate movingparts of the axial piston engine. It is moreover advantageous when theleakage fluid is present as a film between the seating surfaces of partswhich are not movable relative to one another, thereby preventing or atleast reducing contact corrosion and abrasion resulting from vibrations.It is further advantageous when the hydraulic fluid may travel with aslittle hindrance as possible to the desired lubricating points. This isnot guaranteed when in the housing interior there is a barrierpreventing a desired feed of the fluid to the lubricating point. Such abarrier is formed by a multitooth coupling between two parts of theaxial piston engine in the housing interior of the latter. The purposeof a multitooth coupling is to connect two parts rigidly to one another,e.g. prevent them from rotating relative to one another. In the axialpiston engine of the initially indicated type, such a multitoothcoupling may be provided between a driving shaft and a cylinder drummounted thereon. Since a multitooth coupling is to transmit considerablecoupling forces, the aim is to fashion the mutually adjacent surfaces ofthe multitooth coupling not only in the region of the tooth flanks andthe tooth spaces in such a way that they fit substantially tightlyagainst one another. As a result, the multitooth coupling forms a liquidbarrier, which prevents or at least reduces the access of the hydraulicfluid to both sides of the multitooth coupling.

From the previously mentioned DE 32 22 210 A1 it is also known for asupport ring, which is mounted on the driving shaft and has a sphericalsegment-shaped support surface for a retaining plate for holding backsliding pads, to be positioned in the operating position by means ofaxially disposed thrust pins lying opposite one another on the peripheryof the driving shaft, wherein the thrust pins are mounted in a slidingdisplaceable manner in bores, which extend in the region of themultitooth coupling between the support ring at the one side of themultitooth coupling and a thrust ring at the other side of themultitooth coupling. The thrust ring is biased by a pressure springtowards the thrust pins and towards the support ring, wherein the end ofthe pressure spring remote from the thrust ring biases the cylinder drumelastically towards a cam disk. In said development too, the multitoothcoupling forms a barrier preventing the fluid from flowing from the oneside of the multitooth coupling to the other. In the known developmentthis is particularly problematical because the fluid is prevented fromflowing into an annular clearance zone between the driving shaft and thecylinder drum. A rolling-contact bearing disposed in the region of a camdisk and provided for mounting the driving shaft rotatably on therelevant housing wall is therefore cut off from being intensivelyflushed, lubricated and cooled by the hydraulic fluid.

Furthermore, the gearing is weakened if the bores for the thrust pinsextend right through the middle of the teeth or if a tooth is left outin the region of a thrust pin. DE 198 28 429 A1 describes an axialpiston engine having a return apparatus comprising thrust pins, which issimilar to the previously described return apparatus. In said previouslyknown development, three thrust pins arranged so as to be distributedover the periphery are displaceably mounted in each case in a firstthrough-channel, which is disposed in the root region of a missing toothof the cylinder drum. In said non-generic development, the missing teethform two through-channels for the fluid. In said development too, thestability and/or strength of the toothed ring coupling is impairedbecause of the missing teeth.

SUMMARY OF THE INVENTION

The underlying object of the invention is to develop an axial pistonengine of the initially indicated type in such a way that, whilesimultaneously guaranteeing a stable construction, the multitoothcoupling enables a flow penetration and/or a mechanical penetration fromone side of the multitooth coupling to the other.

Said object is achieved by the features as described herein.Advantageous developments of the invention are described in thesub-claims.

In the construction according to the invention a flow of fluid throughthe through-channel from one side of the multitooth coupling to theother is possible so that in the operating mode the fluid reaches bothsides of the multitooth coupling and the lubrication in said regions isguaranteed. Since the at least one through-channel according to theinvention is disposed in a tooth tip surface and/or in an opposing toothspace bottom surface, it is situated in a region which is insensitive toweakening and the flanks of the teeth and/or tooth spaces areunimpaired.

As the main load zone of the multitooth coupling is situated in theregion of the flanks, the construction according to the invention leadsneither to a substantial weakening of the cross section of the teeth norto a reduction of the compressive load per unit area. The stability andendurance of the multitooth coupling are therefore maintained despitethe presence of one or more through-channels arranged so as to bedistributed over the periphery.

For fluidic reasons it is advantageous to dispose a plurality ofthrough-channels preferably so that they are distributed uniformly overthe periphery of the gearing. It is also possible to dispose thethrough-channel only in one of the mutually opposing tooth tip surfaceand tooth space bottom surface or in a mutually opposing manner in bothsurfaces. The latter leads to a common through-channel of enlarged crosssection.

The cross-sectional shape of the at least one through-channel may differand be adapted to constructional conditions. A rounded or half-round orU-shaped cross-sectional shape is advantageous for avoiding a notcheffect. The cross-sectional shape may however also be polygonal orhollow wedge-shaped, this being advantageous for reasons of manufactureand for additional reasons explained further below.

The at least one through-channel according to the invention may howeveralso be used to receive a pin as part of the axial piston engine, e.g. apreviously described thrust pin extending between two axially movablecomponents disposed on either side of the multitooth coupling, e.g.between a pressure spring and a support ring for a return device. Thethrust pin penetrates the through-channel and may, for example, beguided slidingly therein with slight motional clearance. In said case,the through-channel is used not to create a flow connection between bothsides of the multitooth coupling but to enable a mechanical connectionextending through the through-channel and, indeed, likewise withoutsubstantially impairing the stability of the gearing.

In said case, the pin may be slideably guided in the through-channelwith slight motional clearance, so that a fluid penetration is notprovided. When the at least one through-channel is designed with a crosssection sufficiently larger than the pin, the construction according tothe invention may form a passage both for the mechanical connection andfor the fluid.

The through-channel is open towards the tooth tip surface and/or toothspace bottom surface. The advantage of said construction is that the atleast one through-channel may be manufactured easily and inexpensivelyin the form of a groove, e.g. by a cutting operation using a slottingtool, a broaching tool, a roller-type hammering tool or a milling tool,especially with inclusion of the profile in the milling cutter geometry.

BRIEF DESCRIPTION OF THE DRAWINGS

There now follows a detailed description of the invention and furtheradvantages achievable thereby by way of preferred constructions of anadvantageous embodiment. The drawings show:

FIG. 1 an axial section through an axial piston engine according to theinvention;

FIG. 2 the partial section II—II in FIG. 1 with several modifiedconstructions;

FIG. 3 a section corresponding to the partial section in a furthermodified construction;

FIG. 4 an axial section through an axial piston engine according to theinvention in a further modified construction;

FIG. 5 the partial section V—V in FIG. 4;

FIG. 6 a section corresponding to the partial section V—V in modifiedconstructions and

FIG. 7 a section corresponding to the partial section V—V in furthermodified constructions.

DETAILED DESCRIPTION OF THE INVENTION

The axial piston engine 1 illustrated by way of example has a closedhousing 2 comprising a pot-shaped housing part 3, the housing interior 4of which is closed detachably by means of a so-called connecting part 5,which is fastened in the sense of a lid to the free edge of the housingpart 3 by means of screws 6, which are implied in the drawing. Mountedrotatably in the housing 2 is a driving shaft 7, which penetrates thebottom wall 3 a of the pot-shaped housing 3 in a bearing hole 8 and issupported in a freely rotatable manner by rolling-contact bearings 9, 11indirectly or directly against the bottom wall 3 a of the pot-shapedhousing 3 in a bearing hole 8 and is supported in a freely rotatablemanner by rolling-contact bearings 9, 11 indirectly or directly againstthe bottom wall 3 a of the pot-shaped housing 3 and against theconnecting part 5. Disposed on the inside of the connecting part 5 is acam disk 13 having control channels 14, which extend opposite oneanother substantially parallel to the axis of rotation 7 a of thedriving shaft 7 and are connected respectively to a feed line 15 and adischarge line 16 in the connecting part 5. Adjoining the inside of thecam disk 13 is a cylinder drum 17, which is seated by means of an oblonghole 18 on the driving shaft 7 and connected thereto so as to berotatably in conjunction therewith by means of a multitooth coupling 19,which in the present embodiment is disposed only in an end region of thecylinder drum 17 remote from the cam disk 13 and in a longitudinalregion of the driving shaft 7 radially adjacent to said end region.

A plurality of substantially paraxially extending piston bores 21 aredisposed in the cylinder drum 17 so as to be distributed over theperiphery and are connected at their ends facing the control channels 14by tapered feed and discharge channels 22 to the control channels 14 andopen out of the cylinder drum 17 at the end remote from the cam disk 13.Supported in an axially reciprocating manner in the piston bores 21 arepistons 23, which with their ends facing the cam disk 13 delimit workingchambers 24 in the piston bores 21 and with their top ends remote fromthe cam disk 13 project from the cylinder drum 17 and are axiallysupported by means of supporting joints 25, in particular ball joints,in an obliquely extending transverse plane against an inclined plate 26.In the case of a present, swash plate-style axial piston engine 1, theinclined plate 26 is formed by a so-called swash plate, which ismounted, in an axial piston engine 1 with a fixed throughput rate,rigidly and, in an axial piston engine 1 with a variable throughputrate, pivotally about a swivelling axis 27 extending at right angles tothe axis of rotation 7 a and is adjustable by means of an, as such,known and non-illustrated adjusting apparatus and lockable in theposition adjusted in each case. For said purpose, hollow cylindersegment-shaped bearing surfaces 31 a on the swivel plate and on a pivotbearing may be used. The swash plate at its side facing the cylinderdrum 17 has an inclined surface 26 a, against which the pistons 23 aresupported by means of sliding pads 29, which are connected by thesupport joints 25 to the top ends of the pistons 23 so as to be capableof swivelling in all directions.

In the present embodiment, the swash plate 26 is mounted on the bottomwall 3 a, wherein for said purpose a bearing ring 31 may be provided,which is supported against the bottom wall 3 a and has a bearing hole,in which the associated rolling-contact bearing 9 is mounted. Disposedin the swash plate 26 is an axial through-hole, through which thedriving shaft 7 extends with motional clearance.

In the operating mode of the axial piston engine 1 the driving shaft 7and the cylinder drum 17 rotate jointly about the axis of rotation 7 a,wherein the pistons 23 because of the inclined plane on the swash plate26, here on the inclined surface 26 a, are displaced to and fro in thepiston bores 21. In said case, the axial piston engine 1 may operate inthe pump mode or in the motor mode. To prevent the sliding pads 29 fromlifting off the inclined surface 26 a, there is associated with thesliding pads 29 a return apparatus 33, which keeps the sliding pads 29applied against the inclined surface 26 a and, in the presentembodiment, is formed by a return disk 33 is axially supported by aspherical segment-shaped concave bearing surface 37 against acorrespondingly spherical segment-shaped convex bearing surface 38 of asupport ring 39, which is mounted by means of a bearing hole 41 in anaxially displaceable manner on the driving shaft 7 and supported in thedirection of the cylinder drum 17 by a force, which is greater than thelift-off forces. The support ring 39 is preferably connected by a secondmultitooth coupling 19 a to the driving shaft 7, so as to be rotatablein conjunction therewith, wherein the teeth 43 a may be provided jointlyfor both multitooth couplings and may be correspondingly long.

In order to achieve efficient sealing between the cylinder drum 17 andthe cam disk 13, it is advantageous to bias the cylinder drum 17 with anaxial elastic force towards the cam disk 13. In the embodiment accordingto FIG. 1, contact pressure forces for the sliding pads 29 and thecylinder drum 17 are generated by means of a common, axially effectivespring 42, which may be disposed e.g. between the support ring 39 andthe cylinder drum 17 and presses said parts apart from one another.

As may be seen particularly in FIG. 2, the multitooth coupling 19comprises a plurality of teeth 43 a, 44 a and tooth spaces 43 b, 44 b,which are disposed on the lateral surface of the driving shaft 7 and onthe inner lateral surface of the cylinder drum 17 respectively andarranged in a regular alternating sequence in each case in peripheraldirection and of which the main shape and size are in each case designedin such a way that the teeth substantially fill the tooth spaces. Duringthe rotational coupling in the operating mode the teeth are loaded ineach case in peripheral direction, wherein pressure forces acting inperipheral direction are transmitted and generate a specific compressiveload per unit area at the tooth flanks 43 c, 44 c delimiting the teeth43 a, 44 a. The surfaces extending between the flanks 43 c, 44 c aredenoted by tip surfaces 43 d, 44 d and tooth space bottom surfaces 43 e,44 e.

By virtue of the shaping described thus far, the multitooth coupling 19because of the relatively close contact forms a blocking wall or barrierpreventing a flow of the fluid between the interior portions 4 a, 4 bdisposed on either side of the multitooth coupling 19. In order toenable a flow and hence an exchange of fluid between the interiorportions 4 a, 4 b, the gearing has, preferably in the middle of at leastone tooth tip surface 43 d, 44 d and/or at least one tooth space bottomsurface 43 e, 44 e of the driving shaft 7 and/or of the cylinder drum17, a through-channel 45, which therefore connects the two interiorportions 4 a, 4 b to one another so that a flow may occur. By said meansthe lubrication of respective associated surfaces is improved and wear,abrasion and contact corrosion are prevented or at least reduced. Whenone interior portion 4 a, 4 b is connected to a leakage outlet, thethrough-channel is also used to connect the other interior portion 4 bto the leakage outlet.

The at least one through-channel 45, because of its opening out towardsthe associated tip surface or bottom surface 43 d, 44 d, 43 e, 44 e, hasa groove which may be manufactured in one working step with the toothprofile, e.g. by means of a broaching, slotting or roller-type hammeringtool. In order to enlarge the cross-sectional area of thethrough-channel 45, it is advantageous to dispose through-channels 45radially opposite one another in both mutually opposing tooth tipsurfaces 43 d and/or 44 d and tooth space bottom surfaces 43 e and/or 44e. When a plurality of through-channels 45 are arranged opposite oneanother or on their own and distributed over the periphery, theeffective flow cross section may be increased further.

The cross-sectional shape of the at least one through-channel 45 may berounded (FIGS. 2 and 5) or curved in the shape of a circular arc segment(FIG. 7) or polygonal (FIGS. 3 and 6), e.g. square or triangular. Insaid case, the through-channels 45 may be disposed in the tooth tipsurfaces 43 d, 44 d and/or in the tooth space bottom surfaces 43 e, 44 eof the driving shaft 7 and/or of the cylinder drum 17 so as to succeedone another directly in peripheral direction or to skip one or moretooth tip surfaces 43 d, 44 d and/or tooth space bottom surfaces 43 e,44 e. The embodiments described above and yet to be described may beused either in combination or each on their own.

In the embodiments according to FIGS. 4 to 7, in which identical orcomparable parts are provided with identical reference characters, thespring 42 is disposed at the side of the multitooth coupling 19 facingthe cam disk 13 in an annular space disposed between the cylinder drum17 and the driving shaft 7 and is preferably formed by a cylindricalhelical spring, which with its end facing the cam disk 13 pressesagainst an inner shoulder surface 47 of the cylinder drum 17 and biasesthe latter towards the cam disk 13. The end of the spring 42 remote fromthe cam disk 13 biases the return apparatus 33 by means of a pluralityof mutually opposed axial thrust pins 48, which extend in each casethrough a through-channel 45 as far as the support ring 39. A thrustring 49 may be disposed between the thrust pins 48 and the spring 42.The length of the thrust pins 48 is greater than the axial length of themultitooth coupling 19 so that they project into the annular space 46. Aplurality of thrust pins 48 distributed over the periphery and aplurality of through-channels 45 for receiving them are provided inorder to distribute the axial contact pressure over the periphery.

In said embodiments, the through-channels 45 form axial guides for thethrust pins 48. When the shape and size of the cross section of thethrough-channels 45 is adapted with a slight motional clearance to theshape and size of the cross section of the thrust pins 48, thethrough-channels 45 exclusively perform a guide function for the thrustpins 48. In such a case, by means of another flow passage it may beensured that the fluid passes from the one housing interior portion 4 ato the other 4 b, here into the annular space 46 and to therolling-contact bearing 11, in order to lubricate and optionally alsocool and/or flush said region. An adapted cross-sectional shape arises,for example, when two e.g. half-round through-channels 45 are disposedopposite one another, into which a common round or square thrust pin 48is inserted with slight motional clearance, as is shown on the right inFIG. 7.

It is advantageous to construct the through-channels 45 in such a waythat they both perform a guide function for the thrust pins 48 and format least one passage for the fluid. This may be achieved in that thenumber of through-channels 45 is greater than the number of thrust pins48 and so at least one through-channel 45 may be used as a free passage.This may however also be achieved in that the cross-sectional shape ofthe through-channels 45 differs from the cross-sectional shape of thethrust pins 48. A suitable choice for said purpose is a polygonal shapefor the through-channels 45 and a round shape for the thrust pins 48. Insaid case also, mutually opposing through-channels 45, which are e.g.polygonal in cross section, may receive a common thrust pin 48 of adifferent, e.g. round cross-sectional shape, as is shown on the left inFIG. 7. In said case, the through-channels 45 may perform a guidefunction for the thrust pins 48 in that the latter are linearly guidedand free through-channel cross sections 45 a remain, through which aflow of fluid may occur.

A common feature of all of the embodiments according to the invention isthat a weakening of the tooth flanks 43 c and 44 c is avoided. Since noteeth 43 a, 44 a are omitted, despite the through-channels 45 aneffective connection between driving shaft 7 and cylinder drum 17 iscreated.

What is claimed is:
 1. Axial piston engine (1) having a housing (2), thehousing interior (4) of which contains a cylinder drum (17) and a swashplate (26) disposed axially adjacent to the latter, wherein disposed inthe cylinder drum (17) and extending substantially parallel to thecenter line of the latter is a plurality of piston bores (21), in whichpistons (23) are displaceably guided, of which the piston ends facingthe swash plate (26), wherein a driving shaft (7) is rotatably mountedin the housing (2) and is connected to said cylinder drum so as to berotatable in conjunction therewith by a multitooth coupling (19) havinga regular alternating arrangement of mutually meshing teeth (43 a, 44 a)and tooth spaces (43 b, 44 b) in peripheral direction, and whereindisposed in the region of the multitooth coupling (19) is at least onethrough-channel (45), which extends substantially parallel to the axisof rotation of the driving shaft (7) and from the one side of themultitooth coupling (19) to the other, characterized in that thethrough-channel (45) is disposed between at least one tooth tip surface(43 d, 44 d) and a tooth space bottom surface (43 e, 44 e) lyingopposite the tooth tip surface such that a pin having a circular radialdimension can be placed in the through channel such that the radialcenter of the pin is positioned substantially equidistant from a top ofthe tooth tip surface and a bottom surface of the tooth space bottomsurface.
 2. Axial piston engine according to claim 1, characterized inthat the cross-sectional shape of the at least one said through-channel(45) is rounded or U-shaped.
 3. Axial piston engine according to claim1, characterized in that the cross-sectional shape of the at least onesaid through-channel (45) is selectively polygonal, triangular orsquare.
 4. Axial piston engine according to one of the preceding claims,characterized in that the at least one said through-channel (45) extendsin bath mutually opposing tooth tip surfaces (43 d) and tooth spacebottom surfaces (44 d).
 5. Axial piston engine according to claim 1,characterized in that a plurality of said through-channels (45) areperipherally spaced about said multitooth coupling and are disposed eachrespectively in a tooth tip surface (43 d, 44 d) and/or a tooth spacebottom surface (43 e, 44 e).
 6. Axial piston engine according to claim5, characterized in that a thrust pin (48) is disposed as part of amechanical penetration and/or connecting apparatus in each of aplurality of said through-channels (45) arranged so as to be distributedover the periphery and being longer than the width of said multitoothcoupling (19).
 7. Axial piston engine according to claim 6,characterized in that the thrust pins (28) are biased by the action of aspring (42) towards a return apparatus (39) for sliding pads (29). 8.Axial piston engine according to claim 6, characterized in that theshape and size of the cross section of the through-channels (45) areadapted to correlate to the shape and size of the cross section of thethrust pins (48) arranged therein.
 9. Axial piston engine according toclaim 6, characterized in that the through-channels (45) and the thrustpins (48) disposed therein have different cross-sectional shapes. 10.Axial piston engine according to claim 6, characterized in that thethrust pins (48) have a round cross-sectional shape.
 11. Axial pistonengine according to claim 6, characterized in that a thrust ring (49) isdisposed between the ends of the thrust pins (48) remote from the returnapparatus (33) and a pressure spring (42) formed by a cylindricalhelical spring.
 12. Axial piston engine according to claim 11,characterized in that the thrust ring (49) and the thrust pins (48) areof an integral construction.
 13. Axial piston engine (1) having ahousing (2), the housing interior (4) of which contains a cylinder drum(17) and a swash plate (26) disposed axially adjacent to the latter,wherein disposed in the cylinder drum (17) and extending substantiallyparallel to the center line of the latter is a plurality of piston bores(21), in which pistons (23) are displaceably guided, of which the pistonends facing the swash plate (26), wherein a driving shaft (7) isrotatably mounted in the housing (2) and is connected to said cylinderdrum so as to be rotatable in conjunction therewith by a multitoothcoupling (19) having a regular alternating arrangement of mutuallymeshing teeth (43 a, 44 a) and tooth spaces (43 b, 44 b) in peripheraldirection, and wherein disposed in the region of the multitooth coupling(19) is at least one through-channel (45), which extends substantiallyparallel to the axis of rotation of the driving shaft (7) and from theone side of the multitooth coupling (19) to the other, characterized inthat the through-channel (45) comprises a groove which is disposedbetween at least one tooth tip surface (43 d, 44 d) and a tooth spacebottom surface (43 e, 44 e) lying opposite the tooth tip surface, and isselectively located in the tooth top surface, in the tooth space bottomsurface, or in both the tooth tip and tooth bottom space surfaces suchthat a pin having a circular radial dimension can be placed in thethrough channel such that the radial center of the pin is positionedsubstantially equidistant from a tot of the tooth tip surface and abottom surface of the tooth space bottom surface.